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http://community.lex18.com/weather/?p=4572
January 22…9:00 am
We’ll just do a quick short written post this morning. I was in the process of doing a video last night, but got sidetracked trying to create a graphic for it (took longer than I wanted) but on the flipside we now have a nifty snow cover map that we can also use on that crazy-nutty TV side.
If you were watching us on the TV Thursday and Friday last week you saw us talking about another storm potential (and that still is the key word) for days 7 and 8 (which as we’ve advanced in time would be Thursday/Friday of this week). At that point last week ALL…and it was ALL of the modelling was screaming that a low this week would be a cutter and head toward the Lakes. Heck, some of the modelling was taking the low toward Minneapolis. On those tracks as we all know so well it puts us in the warm sector and hello rain. However, if you were watching you saw that we had our mix icon and temps in the 30s. Given the amount of Arctic air in play at the moment and the overall look of the atmosphere the idea of a cutter…at least one that extreme…just didn’t look right. Over the course of the weekend we watched as the modelling was trending southeast with each run to the point that most of it was locking in on a track pretty much over us…still not the perfect winter scenario for us, but it’s a whole lot better than Minneapolis.
We continue to say a storm is ‘interesting’ this far out as a 50 mile shift in a storm’s path means the difference in 35 degree rain or children (and teachers) dancing in the streets because the winter wonderland has arrived. What we can determine scientifically (not by wishing) is that there is going to be a storm (and a decent sized one) in the neighborhood at the end of the week. What we do NOT know (and really can’t know until this system emerges into a more data rich environment) is the eventual likely path. You can speculate…you can guess (wildly)…but you do not know. And you know, wild guesses can even be right once in a while, but you wouldn’t want to depend on that or base your life on those (try it in Vegas sometime!…ok maybe not).
Winter events come in all shapes and sizes…the VAST majority are just nuissances…some are disrupitve for a day or so…and a very few are crippling for days at a time. Almost no one mistakes Kentucky’s weather for Michigan’s and no matter how hard it’s wished for it seldom happens. Which leads us up to what’s ahead of us…
We talk about modelling a lot. It has become our primary tool (for good or bad) in forecasting. There are many models out there (and all a model is is a computer program that reduces our atmoshpere down to numbers). Each one looks at the atmosphere differently, thus the differing outputs they come up with. Modelling has also advanced to the point where you run the same basic model with different ‘tweaks’ so that you end up with 30 different versions of the same basic idea (that’s called ensembles). The theory being that the average of 30 is better than 1 stand alone. Several of our models have their own ensemble packages…so different models run with different tweaks…which means there’s a whole lot of data out there.
So where are we going with this today? Beginning this weekend the model we trust the most, the European, has been jumping the low southeastward with each run. In fact it’s gotten to the point where its surface low is now passing south of us…which leaves us on the cold side. It’s now been consistent with that for 4 runs which increases confidence in the forecast. However, at least as of last night it’s now become a major outlier as our shorter range models (the NAM and GFS) give this storm the look of a cutter again. When there is that kind of range, forecast confidence is low, especially when the NAM went that way…but then again we’re talking Thursday night/Friday with this system…still a long way out timewise.
Anyway, here’s the run of the euro last night which gives snow lovers cause for hope…
It’s showing a nice surface low in southeast Kentucky with another small reflection near the Georgia/Alabama line. Notice the blue dashed line…that’s the 540 thickness line (thickness of the atmosphere between the 1000 and 500 mb levels in decameters)…that is usually our rain/snow line approximation. That’s good news for many of us snow lovers if that verifies…although with the low where it is it also brings ice concerns into play.
Here’s the Euro’s temperature map for midday Friday (same time frame as above). This is also something new for us to look at…we used to have to infer its surface temp predictions, but now we have access to actually see it. The bright white line is the 32 degree isotherm. Notice that most (but not all) of Kentucky is below freezing…that doesn’t necessarily mean snow, but it does mean the model is seeing most of us with winter precip…and again this is Model-land.
Now with what you’ve seen from the Euro taking it verbatim it’s good news for winter lovers. However, a model is seldom verbatim at this range (it can be close, but again 50 miles changes everything). Say the low is over Danville instead of of Corbin…then most of us get rain. Say the storm ends up somewhere between Jellico and Knoxville…then we get all snow. This is WHY we just say a storm is ‘interesting’ this far out.
This morning’s model runs will hopefully begin to sharpen the focus…we’ll get a new Euro run sometime around the time we’re on with Kruser (about 2:50 on Newstalk 590, WVLK am) which will also help tell the tale.
We try to be steady…consistent…and most importantly accurate as we watch these events unfold. If a significant winter event is looking more likely, we’ll give you plenty of time to get the bread and milk. Ifnothing else over the last 14 years of forecasting Kentucky’s winter weather we’ve learned that prudence and common sense are the keys and not wild guesses.
This is why we do mostly video blogs now…almost 1100 words and almost an hour, but hopefully this gives you a glimpse into what’s going on with our weather and how we do what we do.
Here’s wishing for the southern track…but know we’ll be forecasting with science later!
Enjoy your cold-cold Tuesday. BTW, we did not get to single digits this morning in Lexington (10)…but pretty much anyone north of I-64 did (curse that lack of snow cover!)
Posted: January 22nd, 2013 under Bill's Blog.
